Ge Xia, d'Avignon D André, Ackerman Joseph J H, Sammons R Douglas
Departments of Chemistry (X.G., D.A.d'A., J.J.H.A.), Radiology (J.J.H.A.), and Internal Medicine (J.J.H.A.), Washington University, St. Louis, Missouri 63130; andMonsanto Company, St. Louis, Missouri 63167 (R.D.S.).
Departments of Chemistry (X.G., D.A.d'A., J.J.H.A.), Radiology (J.J.H.A.), and Internal Medicine (J.J.H.A.), Washington University, St. Louis, Missouri 63130; andMonsanto Company, St. Louis, Missouri 63167 (R.D.S.)
Plant Physiol. 2014 Nov;166(3):1255-68. doi: 10.1104/pp.114.247197. Epub 2014 Sep 2.
Horseweed (Conyza canadensis) is considered a significant glyphosate-resistant (GR) weed in agriculture, spreading to 21 states in the United States and now found globally on five continents. This laboratory previously reported rapid vacuolar sequestration of glyphosate as the mechanism of resistance in GR horseweed. The observation of vacuole sequestration is consistent with the existence of a tonoplast-bound transporter. (31)P-Nuclear magnetic resonance experiments performed in vivo with GR horseweed leaf tissue show that glyphosate entry into the plant cell (cytosolic compartment) is (1) first order in extracellular glyphosate concentration, independent of pH and dependent upon ATP; (2) competitively inhibited by alternative substrates (aminomethyl phosphonate [AMPA] and N-methyl glyphosate [NMG]), which themselves enter the plant cell; and (3) blocked by vanadate, a known inhibitor/blocker of ATP-dependent transporters. Vacuole sequestration of glyphosate is (1) first order in cytosolic glyphosate concentration and dependent upon ATP; (2) competitively inhibited by alternative substrates (AMPA and NMG), which themselves enter the plant vacuole; and (3) saturable. (31)P-Nuclear magnetic resonance findings with GR horseweed are consistent with the active transport of glyphosate and alternative substrates (AMPA and NMG) across the plasma membrane and tonoplast in a manner characteristic of ATP-binding cassette transporters, similar to those that have been identified in mammalian cells.
加拿大飞蓬（Conyza canadensis）被认为是农业中一种重要的抗草甘膦杂草，已蔓延至美国的21个州，目前在全球五大洲均有发现。本实验室之前报道，草甘膦在抗草甘膦加拿大飞蓬中快速液泡隔离是其抗性机制。液泡隔离的观察结果与液泡膜结合转运蛋白的存在一致。用抗草甘膦加拿大飞蓬叶片组织进行的体内³¹P核磁共振实验表明，草甘膦进入植物细胞（胞质区室）具有以下特点：（1）对细胞外草甘膦浓度呈一级动力学，与pH无关且依赖于ATP；（2）受到替代底物（氨基甲基膦酸[AMPA]和N - 甲基草甘膦[NMG]）的竞争性抑制，这些替代底物自身也进入植物细胞；（3）被钒酸盐阻断，钒酸盐是一种已知的ATP依赖转运蛋白的抑制剂/阻断剂。草甘膦的液泡隔离具有以下特点：（1）对胞质草甘膦浓度呈一级动力学且依赖于ATP；（2）受到替代底物（AMPA和NMG）的竞争性抑制，这些替代底物自身也进入植物液泡；（3）具有饱和性。抗草甘膦加拿大飞蓬的³¹P核磁共振研究结果与草甘膦及替代底物（AMPA和NMG）以ATP结合盒转运蛋白的特征方式跨质膜和液泡膜进行主动转运一致，类似于在哺乳动物细胞中已鉴定出的转运蛋白。
